''Eohyrax'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of Notoungulate, belonging to the suborder

Typotheria Typotheria is a suborder of the extinct mammalian order Notoungulata and includes five families: Archaeopithecidae, Campanorcidae, Interatheriidae, Mesotheriidae, and Oldfieldthomasiidae. CifelliCifelli, Richard L. 1993. The phylogeny of the nat ...

. It lived during the Middle Eocene, and its remains were discovered in South America.

Description

This animal is mostly known from fossils of its dentition, which suggests it was an animal between the size of a

racoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...

and a

red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the Order (biology), order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe ...

; it would have looked like a marmot from comparison with its better known relatives, such as '' Archaeohyrax''. It had very high-crowned (hypsodont) teeth in its cheek region.

Classification

The genus ''Eohyrax'' was first described in 1901 by Florentino Ameghino, based on fossils found in Late Eocene terrains of Argentina. Ameghino thought the fossils dated from the Late Cretaceous, and this assumption was only corrected much later. Similarly, Ameghino thought that some of the South American mammals he described were the ancestors of the fauna of other continents, and therefore considered ''Eohyrax'' as a relative of

hyrax Hyraxes (), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Typically, they measure between long and weigh between . They are superficially simil ...

es, hence its name, ''Eohyrax'', meaning "Hyrax of the dawn". The real affinities of ''Eohyrax'' within Notoungulata were only recognized later, as it was reclassified as a member of the subgroup of rodent-like notoungulates

. ''Eohyrax'' was approached of the genus '' Archaeohyrax'' within

Archaeohyracidae Archaeohyracidae is an extinct family of notoungulate mammals known from the Paleocene through the Oligocene of South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a ...

a family thought to be ancestral to

Hegetotheriidae Hegetotheriidae is an extinct family of notoungulate mammals known from the Oligocene through the Pliocene of South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a r ...

; however, further researches tend to indicate that Archaeohyracidae are a paraphyletic group, and that ''Eohyrax'' itself would be a basal member of a clade including

Mesotheriidae Mesotheriidae ("Middle Beasts") is an extinct family of notoungulate mammals known from the Oligocene through the Pleistocene of South America. Mesotheriids were small to medium-sized herbivorous mammals adapted for digging. Characteristics Meso ...

and

. Various species have been attributed to the genus ''Eohyrax'' ; after the type species ''Eohyrax rusticus'', Ameghino described ''E. brachyodus'', ''E. isotemnoides'', ''E. platyodus'' and ''E. praerusticus''. It is probable that several of these species were in fact identical to the type species.

Bibliography

*F. Ameghino. 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie reliminary notes on new ungulates from the Cretaceous terrains of Patagonia Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429 *F. Ameghino. 1902. Notices préliminaires sur des mammifères nouveaux des terrains Crétacé de Patagonie {preliminary notes on new mammals from the Cretaceous terrains of Patagonia]. Boletin de la Academia Nacional de Ciencias de Córdoba 17:5-70 *F. Ameghino. 1904. Nuevas especies de mamíferos, cretáceos y terciarios de la República Argentina ew species of mammals, Cretaceous and Tertiarty, from the Argentine Republic Anales de la Sociedad Cientifica Argentina 56–58:1-142 *G. G. Simpson. 1967. The beginning of the age of mammals in South America. Part II. Bulletin of the American Museum of Natural History 137:1-260 *G. Billet, B. Patterson, and C. Muizon. 2009. Craniodental anatomy of late Oligocene archaeohyracids (Notoungulata, Mammalia) from Bolivia and Argentina and new phylogenetic hypotheses. Zoological Journal of the Linnean Society 155:458-509 *Billet, Guillaume (2011). "Phylogeny of the Notoungulata (Mammalia) based on cranial and dental characters". Journal of Systematic Palaeontology. 9 (4): 481–97. doi:10.1080/14772019.2010.528456. OCLC 740994816. {{Taxonbar, from=Q56254967 Typotheres Eocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 1901 Prehistoric placental genera Golfo San Jorge Basin Sarmiento Formation